Conventionally, a fuel supplying controller includes a fuel tank accommodating fuel, a supply pump drawing the fuel from the fuel tank and supplying the fuel to an internal combustion engine, and a fuel filter provided in a passage between the fuel tank and the supply pump to remove foreign matters in the fuel.
In the fuel supply controller, foreign matters of the fuel drawn from the fuel tank are removed by the fuel filter. Therefore, the fuel filter is clogged, and the fuel is improperly supplied to the supply pump from the fuel tank. The fuel supply controller is provided with a clogging detection portion detecting a clogging of the fuel tank. When the fuel filter is clogged by the foreign matters, the clogging detection portion detects the clogging of the fuel tank by measuring a fuel pressure of the fuel drawn by the supply pump. Further, a driver is noticed by a warning portion that the fuel filter is clogged, and then exchanges the fuel filter.
It is known that a viscosity of fossil fuel used in the internal combustion engine varies according to the fuel temperature. For example, gas oil (light oil) used in a diesel engine varies according to the fuel temperature. When the fuel temperature becomes lower, the viscosity of the fuel becomes higher. In other words, the high-viscosity change of the fuel is generated. When the fuel having high viscosity flows through the fuel filter, a pressure loss of the fuel becomes larger according to the fuel filter. A pressure of the fuel drawn by the supply pump is lowered by the pressure loss. Thus, the clogging detection portion may erroneously determine that the fuel filter is clogged due to the pressure loss, even though no foreign matter clogs at the fuel filter.
JP-2005-273535A discloses a clogging detection portion of a fuel supplying controller previously sets a non-detection period where a clogging detection is prohibited at a predetermined time period. An elapsed period is counted by a timer counter which adds at a predetermined period. When the timer counter exceeds the non-detection period, the clogging detection is started. Even when a temperature sensor provided between the fuel tank and the supply pump to detect the fuel temperature is canceled, the increase in fuel temperature can be measured, and the clogging detection can be prohibited in a case where the high-viscosity change of the fuel is generated. Since the clogging detection is executed after the high-viscosity change of the fuel is canceled, an erroneous determination can be prevented.
Since the fuel is accommodated in the fuel tank provided at a position separating from the internal combustion engine, the fuel temperature of the fuel tank is readily affected by an ambient temperature. Therefore, an increasing rate of the fuel temperature is affected by a specified vehicle-state value of the internal combustion engine and an outer environment.
According to JP-2005-273535A, since the non-detection period is only set based on the specified vehicle-state value such as a vehicle speed or an engine speed, it is possible that the increasing rate of the fuel temperature is erroneously measured. In this case, the clogging detection portion may not start the clogging detection even though the high-viscosity change of the fuel is actually canceled, or the clogging detection portion may start the clogging detection even though the high-viscosity change of the fuel is generated. Therefore, the clogging detection portion cannot guarantee the reliability of the clogging detection.